Photonic bandgap structures, known as PBG structures, are periodic structures that prevent the propagation of a wave for certain frequency bands. These structures were firstly used in the optical field but, in recent years, their application has been extended to other frequency ranges. Thus, they are used in particular in microwave devices such as antennas, filters, waveguides, etc. The use of a photonic bandgap structure with a line produced in microstrip technology is described for example in the article “Novel 2-D photonic band gap structure for microstrip lines” published in the journal IEEE Microwave and Guided Wave Letters, Vol. 8, No. 2, Febuary 1998. This article describes a photonic bandgap structure consisting of discs etched on the opposite side of the substrate to that receiving the microstrip line. This structure allows a filter to be produced.
In the case of microstrip lines or patch-type antennas, the PBG structures are mainly obtained either by etching periodic patterns, obtained by demetallizing the earth plane of the structure produced in microstrip technology as described above, or by periodically drilling the substrate comprising the circuits in microstrip technology while still maintaining the continuity of the earth plane. The structures already described in the prior art offer many possibilities, especially for filtering.